Wireless communication systems, such as the 3rd Generation (3G) of mobile telephone standards and technology, are well known. An example of such 3G standards and technology is the Universal Mobile Telecommunications System (UMTS™), developed by the 3rd Generation Partnership Project (3GPP™) (www.3gpp.org). The 3rd generation of wireless communications has generally been developed to support macro-cell mobile phone communications. Such macro cells utilise high power base stations (NodeBs in 3GPP™ parlance) to communicate with wireless communication units within a relatively large geographical coverage area. Typically, terminal devices (sometimes referred to as wireless communication units, or User Equipment (UEs) as they are often referred to in 3G parlance), communicate with a Core Network (CN) of the 3G wireless communication system via a Radio Network Subsystem (RNS). A wireless communication system typically comprises a plurality of radio network subsystems, each radio network subsystem comprising one or more cells to which UEs may attach, and thereby connect to the network. Each macro-cellular RNS further comprises a controller, in a form of a Radio Network Controller (RNC), operably coupled to the one or more Node Bs, via a so-called Iub interface.
The 3GPP has subsequently defined a further generation of mobile telephone standards, known as Long Term Evolution (LTE), which is commonly referred to as 4G. In LTE, a base station is known as an Evolved Node B (abbreviated to eNodeB or eNB). An eNB connects directly to the LTE core network, which is known as the Evolved Packet Core (EPC), there being no equivalent in LTE of the 3G RNC.
Lower power (and therefore smaller coverage area) cells are currently referred to as ‘small’ cells, with the term femto cells or pico cells typically reserved to refer to a residential small cell. Hereafter, the term small cells will be used to encompass femto cells, pico-cells or similar. Small cells are effectively communication coverage areas supported by low power base stations (otherwise referred to as Access Points (APs) with the term Home Node Bs (HNBs) identifying femto cell access points). These small cells are intended to augment the wide area macro network and support communications to UEs in a restricted, for example indoor, environment. An additional benefit of small cells is that they offload traffic from the macro network to small cells, thereby freeing up valuable macro network resources.
Typical applications for such small cell base stations include, by way of example, residential and commercial (e.g. office) locations, communication ‘hotspots’, etc., whereby HNBs can be connected to a core network via, for example, the Internet using a broadband connection or the like. In this manner, small cells can be provided in a simple, scalable deployment in specific in-building locations where, for example, UEs may come into close proximity to a small cell base station. Small cell base stations are intended to enhance the coverage of a UMTS™ Radio Access Network (RAN) within residential and/or private commercial environments, and it is planned that the number of small cell base stations in a macro cell may number thousands.
The 3GPP Standards for UMTS specify a use of T3212 and/or T3312 timer values. These timer values are broadcast by a cell in its system information or received from the Core Network (CN). The T3212 timer value specifies how often a UE in the cell should perform a location update. The T3312 timer value specifies how often a UE in the cell should perform a routing area update. T3212 is broadcast by a cell in its system information. T3312 is not broadcast in system information, but is instead sent by the core network to a specific UE in GMM Attach Accept and GMM Routing Area Update Accept messages. Similarly, the 3GPP standards for LTE specify the use of a timer T3412. The T3412 timer value specifies how often a UE in an LTE cell should perform the periodic tracking area update procedure. The value of timer T3412 is sent by the EPC to a specific UE in Attach Accept and Tracking Area Update Accept messages.
The interval between periodic location/routing/tracking area updating procedures is typically configured by the network operator. These location update, routing area update and tracking area update procedures provide opportunities for the network to collect measurement information from a UE. However, the T3212, T3312 and T3412 timer values are usually configured to longer periods than is desirable for the purpose of collecting measurement information.
Radio parameter settings for macro networks are typically set by the network operator by a process of “cell planning”, which uses a model of the cell deployment to predict coverage and capacity with different parameter values. They typically back this up with drive testing, where they measure actual RF signal strength and quality as well as service performance. These approaches are possible because the location and environment of each macro cell is known; this is not the case with small cells. The (potentially) very large number of small cells and the fact that they are typically deployed in private residences means that it is not feasible for the operator to determine the RF parameters for each cell individually, Therefore small cells have to be self-configuring either individually or in conjunction with each other—this technology is known as Self-Organising Networks (SON).